drm/amdgpu/navi10: implement GFXCLK_CURVE overdrive

[Why]
Before this patch, there was no way to set the gfxclk voltage curve in
the overdrive settings for navi10 through pp_od_clk_voltage

[How]
Add the required implementation to navi10's ppt dpm table editing
implementation, similar to the vega20 implementation and interface.

Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Matt Coffin <mcoffin13@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>